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TR4A Horn relay


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Hi Guys,

I seem to have an original  Horn relay that's not working. How to check? As I understand it, unlike the 6RA relay that has W1, W2 = 12v supply /earth (switch),  and C1, C2 to whatever is being connected.

The relay for horns only has C1, C2= 12v supply and load  and W1 which is connected to earth through the horn button to sound the horns. Before I bin the relay and try to source a replacement, what is the simple check. A 6RA will click with power across W1 and W2 which indicates good. Not sure what to do with the Horn relay? Can a 6RA be used instead.

Rich

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According to the info I have, the coil is connected between C2 and W1. 12 v on C2 and earth on W1 should operate the relay so that power is switched to C1. 

You could use the other relay by linking C2 and W2 together to get effectively the same thing. 

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Hello Rich. There was a topic on horn relays posted last year. Below is my reply to that thread. So to test put power to C2 and earth to W1. There should then be a connection between C1 and C2. Very simple inside.

Ah the Lucas 6RA relays. I have spent a lot of time collecting a few of these relays to put on my TR. The horn relay is no longer available from the Triumph suppliers. Mine is an R246 made in Bedworth England. The horn push connects to W1 and then to earth via the horn push. Terminal C2 is power from the battery and C1 goes to the horn. When the horn push is pressed then W1 is earthed and the coil inside the relay is activated and C2 connects to C1. I have a Lucas 33188H 12v 3580 relay that has the 3 terminals that works in this way

So in the absence of a direct replacement you can use another type of Lucas 6RA relay. Beware however because just because it says 6RA doesn't mean it is the right one. 6RA refers to a generic group of relays. The one to find is one with the numbers 33213, 33293 or 33302 followed by a letter. After the numbers it say 12v and then the next 3 or 4 numbers tell you the week and year of manufacture. For example 33213J 12v 4571 or 33293A 12v 568. The mounting bracket should be on the side of the casing what Lucas call H1 type housing. H2 have the bracket on the top and H3 don't have a bracket at all. I believe these relays are also fitted to Triumph Stags. These relays are 'normally open' types which means there is no connection between C1 and C2 until you power up the winding. Note some relays have a double Lucar connector for C1 and some have single but doesn't affect how you wire it up. I think this relay is also the same as part number 142169A or type SRB101 or SRB111.

So fit the 6RA relay to the car. Connect horn push to W2 and connect W1 to power. Connect main power supply to C2 (this has an in line fuse) and C1 to horns.

If you prefer one with the bracket on the end opposite the terminals then the number on the relay will be 33311 (also called SRB112) with maybe a letter D after the number. Wiring will be the same.

Looks better (more period) than the modern plastic types I think.  

Although many early Triumphs didn't have a horn relay I would recommend you use one to protect the horn push circuit that has thinner wires. Try to get the one you have working. They are pretty simple devices.

Beware also that also included under the 6RA 'umbrella' are 24v as well as 12v types and others are normally closed and there are also 'change-over' circuit types.

Keith

Edited by keith1948
corrections
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21 hours ago, RobH said:

According to the info I have, the coil is connected between C2 and W1. 12 v on C2 and earth on W1 should operate the relay so that power is switched to C1. 

You could use the other relay by linking C2 and W2 together to get effectively the same thing. 

 On the original horn relay C1 and C2 is the switched secondary circuit. The horn push is connected to W1 and then to earth when the horn is pressed.  This then closes the contacts inside to connect C1 to C2. Power is supplied to terminal C2 on Lucas 6RA type 33188H 12v. C1 goes to the horn.

Keith

Edited by keith1948
correction
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OK thanks for that Keith and for the details on relay types,  but I'm afraid there is even more confusion generated by your explanation.

Power does not come from the horn push - the horn push connects to earth in all the published diagrams.  It follows that the other end of the winding cannot be earthed internally to the case of the relay as you state.  Perhaps it was in the relay you examined, but if so it is the wrong relay for the application.

Untitled.jpg.c00e4d9a596b291a3f1a7f1109bccb63.jpg

If the other end of the winding is truly earthed internally or if you connect the second winding terminal to earth as you suggest, the relay will never operate. Power has to get to the top of the winding somehow and it isn't coming from the horn push.  In the diagram above ('4A) for a three-terminal relay the winding must be between C2 and W1. That is the only way the circuit can operate as shown.

If C1 and C2 are truly independent it doesn't matter which way round they are connected as you say, but if there is an internal connection to the winding in place of one of the normal winding tabs it certainly will matter since if the live feed is on the wrong one, nothing can ever operate.  Perhaps this is yet another version of the relay that you have not yet found?

A four-terminal relay is shown in the TR6 diagram:

Untitled2.jpg.ceafe83f3be6d9e0e23cd2318cb748f5.jpg

Here you can see that an external link has been made from W1 to C2 to do the same thing since for this relay the windings and the contacts are separate.

 

Edited by RobH
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It's a snip from the Advance Autowire diagram Jim -  the whole thing is here:

http://www.advanceautowire.com/tr24a.pdf

Yes there is an in-line fuse shown between C2 and its feed point (A1 on the control box). 

That oblong box shown in the wire from W1 to the horn push is a connector.

 

Edited by RobH
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Hello Rob

Many apologies. I have just corrected both my posts following your explanations. I have a 6RA 33188H 12v relay that has the 3 terminals W1 C1 and C2. Just to make sure I have removed the metal cover to see exactly what is inside. (Should have done that earlier!). The metal case does not connect to any of the terminals. W1 is the earth (goes to horn push). When I connect the car battery +ve to C2 and -ve to W1 then the coil is activated and C1 is then also connected to C2. C1 as you say then goes to the horns.

Keith

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Thanks Guys for all your responses to my Topic. Seems to have started quite the debate. however having proven that my original relay is defective  (broken wire at base of coil), I have used  a 6RA relay from my come in hand box and wired as a TR6, and the horns work, well with a direct earth from W2:huh:.

Now need to trace and validate the earth through the horn switch/steering column etc. That's for another day!!

Regards

Rich

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Glad you have solved the problem Rich. I have now put my horn relay 6RA back together and rechecked my advice (senior moments?) and decided that I should have a beer. I have a bag full of various Lucas 6RA relays of different numbers but all basically the same with 4 connectors. I only have one spare horn relay with the 3 connectors though. This was a useful diversion from working out the wiring for a 1960's electric guitar and trying to solve a mains hum problem (which I think I have now done).

Keith

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Rob, thanks for the diagram. However that Autowire diagram for the TR4A does have some errors. Here’s a correction to the layout of the light switch.

Jim

 

3D3C52FA-7904-4D54-B473-0853328A9239.jpeg

Edited by Tr4aJim
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Thanks Jim -

 tthompson  has drawn up a corrected version which he posted on this thread (fifth post down):

 

Edited by RobH
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